Home

Hydrologic Cycle as an Ecological Function

What is the hydrologic cycle?

The hydrologic -- or water -- cycle is the continuous movement of water between the earth and the atmosphere. Water reaches land as precipitation such as rain and snow. Then the water evaporates, condenses in the atmosphere to form clouds, and falls to the earth again as precipitation, continuing the cycle.

When water falls to the ground it can collect on the land becoming streams, rivers, lakes, or soaks in to the ground to become groundwater. Plants take up groundwater either using it or releasing it to the atmosphere.

Why is the hydrologic cycle important?

The hydrologic cycle is important because it is how water reaches plants, animals and us! Besides providing people, animals and plants with water, it also moves things like nutrients, pathogens and sediment in and out of aquatic ecosystems.

Ways in which the hydrologic cycle is affected

One of the ways that water moves through the cycle is through its ability to permeate, or soak, into the soil. There are four key areas that impact that part of the cycle: changes in the ability of soil to soak up water through increases of impervious surfaces, like roads and buildings, and removal of forest cover;

water withdrawals or impoundments (such as through wells or dams)

filling depressional wetlands;

and altering stream flows and beds.

Back to top

Large Woody Debris as an Ecological Function

What is large woody debris?

Large woody debris (sometimes abbreviated LWD and also known as driftwood) refers to the fallen trees, logs and stumps, root wads, and piles of branches along the edges of streams, rivers, lakes and Puget Sound.

Why is large woody debris important?

Wood helps stabilize shorelines and provides vital habitat for salmon and other creatures. Preserving and even increasing the amounts of large woody debris along shorelines is important for keeping our aquatic areas healthy and improving the survival of native salmon and other animals in Kitsap County.

Some key benefits of large woody debris to fish and other aquatic creatures:

It provides refuge for juvenile and adult fish at a wide range of river flows, such as flood events.

It creates pools for juvenile fish and hydraulic complexity and roughness along the river bank

It provides food sources and habitat for aquatic insects and wildlife along shorelines.

It helps stabilize shorelines and reduce excessive erosion.

How does large woody debris form?

Large woody debris is delivered to aquatic ecosystems in three main ways:

Windthrow (when wood is blown down in large wind events, such as storms);

Shoreline bank erosion;

Mass wasting, such as landslides.

What interferes with the accumulation and placement of large woody debris?

Shoreline armoring can keep LWD from reaching shorelines or may prevent it from lodging in one place

Reduced water flow (through diversions or withdrawals)

Removal of shoreline vegetation, especially on unstable slopes, can prevent the delivery of wood to shorelines

In some cases, large woody debris is removed when it poses a safety concern in areas of high recreation such as boat launches.

Back to top

Light Energy as an Ecological Function

What is light energy?

Light energy is the natural pathway for light to reach the shoreline and addition of artificial light to the aquatic shorelines, especially at night.

Why is light energy important?

Light energy affects water temperature, biological processes (such as the relationship between predators and prey) and plant photosynthesis and growth. Under natural conditions light is controlled by topography, cloudiness, vegetation cover, and seasonal patterns, like less daylight in the winter.

How do land uses affect light energy?

Natural light can be altered when we remove vegetation, or build structures such as docks and piers that create shade and prevent natural light from reaching the water.

Artificial light is the light we create at night, such as from roads, parking lots, industrial complexes, houses, docks, piers and sports fields. This light can interfere with aquatic animals' routines and change predator-prey relationships.

Back to top

Nitrogen as an Ecological Function

What is nitrogen?

Nitrogen is a naturally occurring element (found in the atmosphere and organic compounds) that occurs in several forms: gaseous nitrogen, ammonium, nitrate, and nitrite. In discussing the ecosystem processes and functions of shorelines, the focus is on nitrate and ammonium.

Why is nitrogen important?

Nitrogen is the biological limiting nutrient in marine systems, generally by being the least available for marine plants and algae. It is similar to phosphorus in freshwater in that when there is too much or too little it can change how an ecosystem functions.

What affects the movement or amount of nitrogen?

Altering wetlands and headwater streams through channelizing or filling can affect the movement of nitrogen.

Nitrogen moves through the watershed in these key areas:

depressional wetlands

headwater streams, and

soil erosion.

Nitrogen can be increased through:

leakage of septic systems;

agricultural and residential impacts such as the application of manure and fertilizers, pet waste, and poor manure management

clearing areas without soil stabilization or without replanting native species. (Some non-native invasive species can increase the amount of nitrogen along shorelines.)

Back to top

Pathogens as a Measure of Ecological Function

What are pathogens?

Pathogens are bacteria and viruses that are destructive to humans and other animals, though they are a natural part of the environment that comes from fecal matter. In high concentration, pathogens can change how an ecosystem functions.

When and where are pathogens a concern?

Pathogens increase in areas with high concentrations of untreated fecal waste, both human and animal. For example, faulty septic systems, livestock manure and goose and pet waste from parks, beaches and expansive lawns can all increase pathogens in water bodies.

What affects pathogen levels?

Wetlands play a key role in filtering out pathogens and sediment in aquatic ecosystems. When wetlands are gone, so is a major way to remove pathogens from the ecosystem.

With an increase of impervious surfaces, and the accompanying decrease in the ability for pathogens (and water) to infiltrate the ground, pathogens move more quickly into aquatic systems and spend less time in environments that increase their mortality.

Channelization of roadside ditches and watercourses also contribute to the quick movement of pathogens from sources to aquatic areas.

Back to top

Phosphorus as an Ecological Function

What is phosphorus?

Phosphorus is a naturally occurring nutrient and under natural conditions enters the water through the weathering of rocks and precipitation of dust. Phosphorus is a limiting nutrient in the freshwater systems of the Puget Sound lowlands area. It is similar to nitrogen in marine environments in that when there is too much or too little it can change how an ecosystem functions. Phosphorus is never truly lost or destroyed; it moves from one system to another.

When is phosphorus problematic?

Increases in phosphorus can lead to problematic changes in freshwater such as increased algae and a subsequent loss of deep water oxygen.

What affects phosphorus levels?

Wetlands slow down water flow and the plants nearby can absorb some of the phosphorus moving through. When wetlands are lost, this ability to remove the phosphorus from the system is eliminated. Phosphorus can also be adsorbed by soils, infiltrate the ground and be adsorbed by soil before entering surface water.

Phosphorus is often increased in streams and lakes by livestock manure, fertilizer from lawns and gardens, pet and goose waste, wastewater flow from faulty septic systems and impervious surface.

Detention ponds, sand filters, and other surface water facilities can intercept or impede phosphorus, but are generally not a complete substitute for natural systems.

Back to top

Sediment as an Ecological Function

What is sediment?

Sediment refers to the particles (such as sand and other soils) which settle, or are deposited, on the sides and bottom of water bodies. It is important in the formation of beaches, spits, sand bars and estuaries and provides substrates for aquatic plants and animals. Sediment also provides nutrients and minerals vital to the health of downstream ecosystems.

Sediment reaches aquatic areas in three main ways:

watershed erosion,

mass wasting events, such as landslides

shoreline erosion.

The key places that sediment comes from are:

steep slopes with unstable or unprotected soils (such as feeder bluffs),

landslide hazard areas,

unarmored channels.

Why is sediment important?

Sediment processes are an extremely important part of many ecosystems, as well as of primary importance to particular species.

For example, various organisms in both marine and freshwater environments rely on replenishment of sediment for their reproductive habitat. Changes to sediment (either too much or too little) can change substrates or cause sediment not to be deposited in the appropriate locations.

What affects the amount of sediment and its movement?

Land uses causing excessive amounts of sediment to enter the aquatic ecosystems and uses causing major reductions in sediment delivery can be detrimental to shorelines.

Land uses that can affect sediment include:

the removal of vegetation on erodable soils, leaving them exposed;

soil disturbance and clearing adjacent to the shoreline;

filling with foreign soils;

roads within 200 feet of the shoreline;

high road density or impervious surface in the basin;

shoreline armoring;

channelization of streams; and

increases in stream flows.

Sediment moves through the ecosystem and is sometimes stored in wetlands, floodplains, streams, lakes, and the banks of the shorelines. The amount of sediment reaching these areas is primarily altered by draining or filling wetlands, loss of shoreline roughness (for example, the removal or loss of large woody debris), channelization of streams, shoreline armoring, dams, and the development of structures like boat ramps and groins which are oriented perpendicular to the marine shoreline. Dredging and bulkheads can also affect how much sediment is present in aquatic shoreline areas.

Back to top

Tidal Influence as an Ecological Function

What are tidal influences?

Tides influence the shoreline environment through the advance and retreat of marine water due to changes in gravitational effects of the moon as the earth rotates each day. In Kitsap County there are two high tides and two low tides of unequal height every day.

What affects tidal processes?

Generally, tides operate at a regional scale and are not controllable at the local level. However, some large scale changes to river hydrology (e.g. diverting and damming) have allowed marine water to reach further up the river because of low fresh water flows.

Further, tidal height can be affected by changes in the sea level over the long term by tectonic subsidence and global warming and over the short term by storm surges and El Nino events.

Tidal influences can be interrupted or lost through changes in beach elevations by shoreline armoring and by artificial tidal restrictions at stream outlets (e.g. culverts, tide gates, and weirs) and along marine shorelines. Shoreline armoring at or below ordinary high water levels physically changes the location where tidal waters have influence, forcing the tidal influence offshore.

The interruption of the tidal influences can prevent the growth of marine vegetation and degrade spawning habitat in estuaries. Tide gates and weirs stop tidal waters from influencing streams and floodplains, either via salinity changes or through backwatering.

Known changes in local tidal influences:

Many of the smaller streams entering Puget Sound have also had their flow regimes altered either through diversions of freshwater for human consumption or through increased levels of impervious surfaces in the basin.

Structures that alter lagoon outlets, especially failing weirs and bulkheads, cause freshwater to back up like a lake during low tides, while simultaneously reducing the duration that salt water has access to the lagoon during high tides. Thus, the tidal movement within the lagoon has been altered.

Back to top

Toxins as a measure of Ecological Function

What are toxins?

Toxins are substances that can be harmful or cause death to plants, animals and humans, usually in an increased amount. There are naturally occurring toxins in the environment: metals such as copper, lead, zinc mercury, cadmium and nickel. Toxic metals are naturally in relatively low concentrations in the Puget Sound lowland streams and lakes.

There are also human-produced toxins such as manufactured herbicides and pesticides and vehicle emissions like gasoline and oil. Other human products, such as antibiotics and artificial hormones, are proving to have toxic effects in aquatic water bodies, as well.

What increases toxins in our environment?

Agriculture, urban development sewage outfalls and internal combustion motor boats can increase concentrations of toxins. Impervious surface and population concentrations contributes to the rate at which toxins move into an aquatic ecosystem.

Toxins come from the application of pesticides, herbicides and other chemicals. Others are associated with motorized vehicles (toxins from internal combustion engines, brake pads, oil leaks, and other vehicles emissions). Sewer outfalls and combined sewer overflows (CSO) also contribute toxins by transporting toxins not treated by sewage plants or collected through stormwater runoff from impervious surfaces such as roads and driveways.

How are toxins naturally prevented from entering our water?

Wetlands slow down water allowing plants to absorb many of the toxins found in aquatic ecosystems. When wetlands are lost, that ability to remove toxins from the system is taken away.

Back to top

Wave Energy as an Ecological Function

What is wave energy?

A wave, measured by its length, period, and height, is energy moving through water. Shorter waves, generated by local winds and vessel wakes, influence the water elevation that already varies with tide and season. Wave energy moves across the water and is ultimately expended on the shoreline, working to erode, transport, and deposit beach sediment. Compared with other locations in the U.S., Puget Sound is considered to be a moderate wave-energy environment.

Under natural conditions, wave energy is primarily generated by localized wind patterns and can be greatly increased during storm events. In addition, waves may be generated by geologic sources (i.e., large-scale bluff collapse, seismic forces). Wave energy is relevant in marine and lake shoreline types.

Why is wave energy important?

Wave energy transfers from the water to the shoreline, helping with the sediment process. In lakes, turn over of thermal stratification also occurs as an interaction between cooling temperatures and wave energy.

Wave energy can be affected by:

high boat traffic

shoreline armoring,

bulkheads and revetments,

jetties and breakwaters,

overwater structures such as docks and piers.

The amount of wave energy or frequency of waves reaching the shoreline can be increased through boat traffic and can increase sediment erosion.

The natural transfer of energy onto the shoreline is altered by shoreline armoring, especially when it is below the ordinary high-water mark. The type and the tidal elevation of shoreline armoring play a strong role in the effect of the alteration.

Hardened armoring approaches, such as bulkheads and revetments, represent the types of shoreline modifications most likely to affect wave-energy regimes. Encroachment of the structure into the intertidal zone also may increase wave energy.

Jetties and breakwaters are designed specifically to decrease wave energy through intervention before it reaches the shorelines. While not generally designed to affect wave energy, docks and piers can also have a similar effect.